Welding timing circuits



Feb. 6, 1940. J. w. DAWSON WELDING mum CIRCUITS Filed May 14, 1937 wrmassas: INVENTOR 6% m 2 50512108 John 14100105072. m3 424 //26 BY Ive/dirty Ngalz'vd r Patented F ll. c, "1940 UNITED STAT WELDING mums: cracnrrs I John W. Dawson, EastMcKeesport, Pa., assig'nor I to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 14, 1937, Serial Nb. 142,564.

13 Claims.

My invention relates to electric control systems, and it has particular relationship to control systems for electric welding.

This application is a continuation in part of my copending application Serial No. 34,003, filed;

July 31, 1935, for Control systems.

It is an object of my invention to provide for accurately applying a predetermined number of cycles of alternating current to a load circuit- Another object of my invention is to provide,

for applying a predetermined number of half cycles of alternating current to a load circuit for performing spot welding operations'and the like.

Another object of my invention is to avoid variation in accuracy of timing because of variation in sources of current.

Other objects and advantages of the invention will be apparent from the following description and drawing, in which:

Figure 1 is adiagrammatic view illustrating 1 the embodiment of my invention in a w circuit; and. h I

.Pig. 2 is a-dlagram illustrating the .:p'o'sitive and negative components applied to the the stop tube.

mergize the other portion of the circuit with the vill eflect the accuracy of the timing of con mi circuit.

It is a specific object of my invention top 'idea starting discharge device and a cut-oil harge device that will have positive and lining components from the same of ergy be ovariamfli n and mummy mm Wm n .fanode lfl oidevice' is is connected to the cathode 512! 'of device It. i ,It will, therefore, be evident that if the vapor electric devices I 8 and i9 are 45 ion in the accuracy of timing dueto any relative ariation between the two sources rhich may not change in proportion.

Referring to the flgures'of the the ei'erence character ll dtes generally;

velding transformer havinga primary I and a secondary winding II. The 'inding I2 is connectedto the lrcuit in which the welding electrodes II, I iagrammatically represented as applied to ob acts "which are to-be welded together; The

rimary winding ll 01 the transformer is congridfot'.

- In-prior art devices utilizing electronic for the control of alternating current audits... application to a load circuit, several devices-have. 1 :een utilized for the initiating and termination" f the electric energy to the load circuit. 'llhese ievices have been arranged, so that one direct iource of energy will energize one portion oi'ithe". :ontrol circuit and another direct source-will nected by means of conductors I6 and il to a source of alternating current.

In order to control the application of the welding current from the source of alternating current to the transformer l0, vapor electric devices shown generally at l8 and I9 are provided. The devices I8 and I9 are of the mercury vapor type having an anode 20 and a mercury pool 2| asa cathode in the bottom of a container 22. In order to render the vapor electric devices I8 10 and i9 conducting, a starting electrode 23 isprovided.

Although other types oi starting electrodes may be utilized, I prefer to use a high resistance felectrode immersed in the mercury and com- 16 posed of carborundum or boron carbide. This type of starting electrode'is well known in the art and is more specifically described in Patent 2,069,283, issued February 2, 1937, to Slepian.

. The two devices It and it are disclosed in or- 20 der that both directions of the alternating cur- 1 rent. maybe controlledin the application to the welding circuit-since each device acts as a rec- 1- tiner' as well as being a controllable conductor.

When-a certain amount of'current is caused to Know throushthe starting dectrode 23 into the mercury pool 2|, a'catho'de spot isiormed which *i'urnishes a source of electrons which in turn ionization of the mercury vapor within the container 2! and underthe influence of positive anode potential. thetube becomes conducting.

it is only;.necessary.to pass suflicient starting' current through thestarting or ignition elec- 23 to form the cathode spot at a predeten nating, current waveto; render the vapor electric conducting iorsthe remainder of that particular half cycle. In, order to conduct succeeding cycles of alternating current, the vapor electric devices it and I! are connected in- 40 That is,;the anode 20 of devices lit-is connected to the cathode 2| 'Voi' device I! and the "energized in turn during successive half cycles,

--current from the source-of alternating current williiow to thetranstorm'er III as long as this condition is maintained. I

The; control system involves the utilization of control tubes tor Supplying ignition current to the discharge in the tubes l8 and I9 and electronic for accurately operating ,and stopping the voperiiition of these tubes at poiutson the'hali cycles of altertime in the cycle in the alter- 35 nating current. In my preferred embodiment illustrated, I utilize tubes 24 and 25 for controlling the discharge in the devices I8 and I9 through the ignitor or starter 23 andthen I uti-' lize a startingtube' 26, a cut-oflf tube 21 for the discharge and in addition for starting the discharge at apredetermined point on the first half cycle of the power period a further tube 28. The application of this control system is preferably instituted by an externally operated switch 28 which may be operated manually or by a cam on the welding machine. In other words, when the operator desires to perform the welding operation, he depresses the switch 29, energizing the relay 30 from the conductors 3|, 32 connected to the source of alternating current. The relay 30, in turn, operates various individual switches hereinafter referred to in the description of the control circuit.

The cathodes of the tubes 24 and 25 are ener-' electrode 23 of the tube I9. The anode 4| of" tube 24 is connected through resistance 31 and switch point 42 of the starting relay 30 to the connection 43 to the anode 20 of tube I8. The anode 44 of tube 25 is likewise connected through resistance 40 and switch 45 of the relay 30 to the connection 46 to the anode 20 of tube IS. The grids 41 and 48 of tubes 24 and 25 are connected through suitable resistances 49 and 50 to opposite ends of the secondary 5| of transformer 52 connected to the source of alternating current. The grids and cathodes of tubes 24 and 25 may be energized from secondary windings on the same transformer instead of the individual transformers disclosed. Between the conductors 43 and 46 extending to the cathodes and anodes of the tubes I8 and I9 previously described is a resistance 53. The variable tap 5.4 on this re-. sistor is to compensate for any slight difierence between the tubes I8 and I9 in operation. The further function of this resistance 53, together with transformer -winding 5|, connecting the grids and cathodes of the tubes 24 and 25 is to nullify the alternating-current potential which would otherwise exist on the grids 41 and 48 of tubes 24 and 25, because of their circuit locations. Resistances 48 and 50 are to limit grid currents, condensers 55 prevent faulty operation of the tubes due to electrostatic pickup of grid by the anode.

Tube 26 is utilized as a starting device. Its cathode 60. is energized through the secondary 6| of transformer 62 and the midpoint '63 of former 1| energized from the source of alternating current. The negative terminal 12 is connected through conductor 13 to the resistance 65, cathode transformer secondary 6| and cathode 60.'. The grid 14 of tube 26 is connected through a connection 15 to the negative terminal 16 of a similar rectifier bridge 11 also energized by the alternating-current source. These rectifler bridges are preferably of the well known copper oxide dry plate type. The negative po-, tential from the rectifier bridge 11 on the grid 14 constitutes a discharge preventing bias normally applied to the control electrode of the starting tube 26 The operation of the starting tube 26 is controlled .by means of the tube 28 previously referred to which controls the point of initiation of tube 26 with respect to the voltage wave. This tube 28is preferably of the hot cathode .gaseous discharge type and is provided with a phase shifting control circuit for the grid 8| of the tube. This phase shifting control circuit comprises an adjustable resistor 82 and an adjustable. capacitor'83. The phase shifting circuit 80 is connected by means of a transformer 84 to the same source of alternating current as is applied to the anode B5 and cathode 86 of the timing tube 26. Alternating current for the timing tube 28 is provided from windings on the secondary of transformer 84. The output of timing tube 28 is applied to a circuit comprising the resistor 81 and a winding 88 of a transformer 89. The secondary winding of the transformer 89 is indirectly connected to the grid 14 of the starting tube 26 when the switch I20 of relay 30 is closed, through the connection 15 which, as previously described, normally applies a negative discharge preventing potential to this grid 14.

The phase shifting circuit 80 is adjusted by means of the variable resistor 82 and variable capacitor 83 to render the start tube 26 conducting at the desired point in the cycle of operation of the alternating current source. The phase shifting circuit 80 will determine th' exact point on the voltage wave that the tube 28 will be rendered conducting. The discharge in tube 28 permits current to flow through the primary winding 88 of transformer 88 and due to the steep wave front of the current applied, a sharp voltage surge will appear in the secondary winding 90 which will be applied, in turn, to the grid 14 of the starting tube 26. The peak valve of the surge is sufficient to overcome the negative potential of the source 11 and to positively bias the grid 14, thereby rendering the start tube 26 conducting. As soon as the start tube 26 becomes conducting, a positive potential is applied to the control tubes 24 and 25 and they will then function to establish the conductivity of tubes I8 and I9.

It will benoted that the cut-off space discharge device 21 has its anode I00 connected through switch IOI to the same positive terminal of the rectifier bridge 10 as the anode 68.0f. thestarting tube 26. The cathode I02 of the cut-off tube 21 is connected through the midpoint I03 of the transformer secondary I04 by means of a connection I05 to the midpoint 54 of the resistance 53 across the anodes and cathodes of the tubes I8 and I9. The grid I06 of cut-off tube 21 is connected through adjustable resistance I01 to the cathode circuit 60 of the starting tube 26,

an adjustable timing condenser I08 is connected to the cathode circuit 63, 60 of starting tube 26.

and conductor 13 extending from the negative terminal of the direct-current rectifier bridge 10 to the resistance 65. The resistance or voltage divider I09 extends from the' connection 99 between the anodes of tubes 26 and 21 to the point 0 to the conductor 13 connected to the grid I06 of tube 21. A tap III is taken from apoint on the cut-oil tube 21.

the potentiometer and by means oi. connection H2 is applied tothe circuit of cathode I02 01 It will be notedthat the point III] with respect to tap III corresponds to the negative grid potential of the cut-oi! tube 21. The point III corresponds to the cathode potential of the tube 21.

The conduction of the tube 26 will apply potential across the resistor 65 and this potential acts to charge the condenser I08 through the variable resistance It". After a time variable between adjustment of resistor III'I, condenser I08 is sufficiently charged to raise the grid I06 of tube 21 to its breakdown point with respect to its cathode I02. With the breakdown of this tube positive potential is fed through the tube and its cathode transformer to wire I 05 which action again throws the bias on control tubes 24 and 25 to a negative value stopping the'further ignition of the tubes I8 and I9 and hence further welding current after the termination of the particular half-cycle.

Leads 66 and I05 are the timing circuit output leads. When neither tube 26 nor 21 is ignited the lead 66 is negative to lead I05. When the starting tube 26 discharges, the lead 66 becomes positive and the lead I05 becomes negative. When the stop tube ignites, the lead 66 again becomes negative in respect to the lead I05. During the period while lead fifi is positive in respect to lead I05, welding current can flow.

The weld has, accordingly, been completed by the automatic operation of tubes accurately timing the predetermined number-of half cycles of alternating current. No manual operation by the operator in connection with the control circuit is necessary after the work I5 is in position, except for the depression of the switch 29. The sequence of the switches operated thereby is first I ill to energize rectifiers I and I1, then 45 and 42 together and then I20. After the weld has been completed, the pressure is released from switch 29 and the various switches operated by relay 30 will be released in reversed order, namely, I20, 42 and 45 and then "II, but the connection at switch II will be made to discharge the timing condenser I08 and have it ready for the next operation.

It will be: noted that both the negative component of the timing voltage applied to tube 21, i. e. between point II 0 and II I, and the positive component of timing voltage, i. e. the voltage across condenser I08, is derived from the same source I0 and, accordingly, variations in this source due to changing of temperature or other causes will equally afiect the positive and negative components of grid voltage as applied to tube 21 and will not change therefore, the accuracy of timing following the discharge of tube 25. This condition is illustrated in Fig. 2 where I2I illustrates the value of the negative component applied from the source III to the grid I" of the stop tube. Curve I22 illustrates the value of the positive component. The welding time starts at I23. During time I24 the condenser III! is charging and at I25 the positive component reaches the value of the negative component and the stop tube 21 is actuated. If, however, the output of rectifier I0 is varied as because of change in temperature, .etc., and I 2| is changed to HP, curve I22 will likewise be corresponding- 1y changed to I22 and the intersection of these two at I25 will be on the same time line I26, thus illustrating that any variation in the source II will not aitect the welding time.

Various condensers and resistances are, or course, illustrated at desired places in the apparatus, some of which, as at H6 and 1, act as filters. It is apparent that many modifications, rearrangement of the number and type of elements and also the application of the control system illustrated may be made without departing from the spirit of the invention. Accordingly, I desire only such limitations to be imposed upon the following claims as is necessitated by the prior art.

I claim as my invention:

1. In acontrol system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the load, a pair of inversely connected space-discharge devices interposed between the'source of alternating current and the load for controlling the flow of current to the load, a control elec- .trode in each of said space-discharge devices, a starting space discharge device for applying an energizing potential to the control electrodes to render said first mentioned space discharge devices conducting, a cut-oil space-discharge de-.

vice for efiecting removal of the energizing potential from the control electrodes to render the pair of space-discharge devices non-conducting, said cut-oil space-discharge device having a control electrode, and a common source of potential for supplying negative and positive components to the control electrode of said cut-off spacedischarge device.

2. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the load, at least one space-discharge device interposedbetween the source of alternating current.

and the load for controlling the flow of current to the load, a control electrode in said space-discharge device, a starting space discharge device for applying an energizing potential to the control electrode to render said first mentioned space discharge device conducting, a, cut-01f space-discharge device for effecting removal of the energizing potential from the control electrode to render the space-discharge device non-conducting and a commo source of potential for energizing the main electrode system of both said starting space discharge device and said cut-01f space-discharge device.

3. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the load, at least one space-discharge device interposed between the source of alternating current and the load forcontrolling the flow of current to the load, a control electrode in said space-dis charge device, a starting space discharge device for applying an energizing potential to the control electrode to render said first mentioned space discharge device conducting, a cut-off space-discharge device for efiecting removal of the energizing potential from the control electrode to render the space-discharge device non-conducting, said cut-oi! space discharge device having a control electrode and a common source of potential for supplying negative and positive componcuts to the control electrode of said cut-oil space discharge device.

4. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the load, a pair of inversely connected space-disthe flow of current to the load, a control electrode in each of said space-discharge devices, a starting space discharge device for applying an energizing potential to the control electrodes to render said first mentioned space discharge devices conducting, a cut-oil space-discharge device for effecting-removal of the energizing potential from the control electrodes to render the pair of space-discharge devices non-conducting and the positive electrodes of said starting space-discharge device and said cut-off space-discharge device being connected together and to a common source of energizing potential for said devices.

5. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the load, a pair of inversely connected space-discharge devices interposed between the source of alternating current and the load for controlling the flow of current to the load, a control electrode in each of said space-discharge devices, a starting space discharge device for applying an energizing potential to the control electrodes to render said first mentioned space discharge devices conducting, a cut-oil? space-discharge device for efiecting removal of the energizing potential from the control electrodes to render the pair of space-discharge devices non-conducting, said cutoff space-discharge device having a control electrode, a source of electrical potential applying a negative component to the last mentioned control electrode and means energized from said last mentioned source of electrical potential for applying a positive component to the last mentioned control electrode of said cut-off space-dis charge device and actuating the same.

6. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the load, a pair of inversely connected space-discharge devices interposed between the source of alternating current and the load for controlling the flow of current to the load, a control electrode in each of said space-discharge devices, a starting space discharge device for applying an energizing potential to the control electrodes to render said first mentioned space discharge devices conducting, a cut-oil space-discharge device for eiiecting removal of the energizing potential from the control electrodes to render the pair of space-discharge devices non-conducting, said cutoff space-discharge device having a' control electrode and a discharge preventing bias normally applied thereto, the positive electrodes of said starting space-discharge device and said cutofi space-discharge device being connected together and to a common source of potential for energizing both said devices, means for initiating the discharge in said starting space-discharge device, and means responsive to the discharge in said starting space-discharge device overcoming the discharge preventing bias on said control electrode of said cut-off space-discharge device.

'7. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating. current to the load, a pair of inversely connected space-discharge devices interposed between the source of alternating current and the load for controlling the flow of current to the load, a control electrode in each of said space-discharge devices, a starting space discharge device for applying an energizing potential to the control electrodes to render said first mentioned space discharge devices conducting, a cut-oil space-discharge device mentioned source of electrical potential for apv plying a positive component to the last mentioned control electrode of said cut-off space-discharge device and actuating the sameafter a predetermined time lag.

8. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the .load, a pair of inversely connected space-discharge devices interposed between the source of alternating current and the load for controlling the flow of current to the load, a control electrode in each of said space-discharge devices, a starting space discharge device for applying an energizing potential to the control electrodes to render said first mentioned space discharge devices conducting, a cut-off space-discharge device for effecting removal of the energizing potential from the control electrodes to render the pair of spacedischarge devices non-conducting, said cut-oil? space-discharge device having a control electrode. a source of electrical potential applying a negative component to the last mentioned control electrode and means energized from said last mentioned source of electrical potential for applying a positive component to the last mentioned control electrode of said cut-off space-discharge device and actuating the same after a predetermined time lag of a number of half-cycles of said first mentioned source of alternating current.

9. In a control system, in combination a source of alternating current, a load, circuit means connecting the source of alternating current to the load, at least one space-discharge device interposed between the source of alternating current and the load for controlling the how of current to the load, a control electrode in said space-discharge device, a starting space discharge device for applying an energizing potential to the control electrode to render said first mentioned space discharge device conducting, a cut-ofi space-discharge device ior effecting removal of the energizing potential from the control electrodes to render the space-discharge devicenon-conducting, said cut-oil space-discharge device having a control electrode and a discharge preventing bias normally applied thereto, the positive electrodes of said starting space-discharge device and of said cut-oil space-discharge device being connected together and to a common source of potential for energizing both said devices, means for initiating the discharge in said starting space-discharge device, and means responsive to the discharge in said starting space-discharge device overcoming the discharge preventing bias on said control electrode of said cut-off space-discharge device after a predetermined time lag of a number of half-cycles of said source of alternating current.

10. In a system applying a source of alternating current to a load, circuit means controlling the application of said source to said load including a starting space discharge device and a cut-off space-discharge device, the'positive electrodes of said devices being connected together and to a common source of energizing potential for said devices.

11. In a system applying a source of alternating current to a load, circuit means controllingthe pplication or said source to said load including a starting space discharge vdevice and a cut-oi! space discharge device, said cut-on space discharge device having a control electrode and a discharge preventing bias normally applied thereto, the positive electrodes of said starting space discharge device and said cut-oil. space discharge device being connected together and to a common source of potential for energizing both said devices, means for initiating the discharge in said starting space discharge device and means responsive to the discharge invsaid starting space discharge device overcoming the discharge preventing bias on said control electrode 01 said cut-.

oil space dmcharge device.

12. In a system applying a source of alternating current to a load, circuit means controlling the application of said source to said load including a starting space discharge device and a cut-oil space discharge device, said cut-oil. space discharge device having a control electrode and a discharge preventing bias normally applied thereto,thepositiveelectrodesotsaidstartingspace devicebeingconnectedtosetherandtoacommon source of potential for energizing both said devices, means for initiating the discharge in said starting space discharge device and means responsive to the discharge in said starting space discharge device overcoming the discharge pre ventinghias on said control electrode of said cutoff space discharge device, said last-mentioned means having a predetermined time lag of a number 0! half cycles of said alternating current.

13. In a system applying a source of alternating current to a load. circuit means controlling the application of said source to said load including a starting space discharge device and a cut-oi! space discharge device having a control electrode, potential means normally applying a negative potential to said control electrode, and means,

charged from said potential means after the actuation of said starting space discharge device, applying a positive potential to said control electrode and actuating said cut-of! space discharge device after a predetermined time delay.

sons w. DAWSON. 

